THE EFFECTS OF RESPIRATORY PATTERN ON THE 0.1-HZ COMPONENT OF R-R INTERVAL VARIABILITY IN MENTAL ARITHMETICS

The 0.1 Hz component of R-R interval variability associated with a spo ntaneous blood pressure rhythm is considered to be a sensitive indicat or of mental load. The aim of this study was to show whether a decreas e in amplitude of the 0.1 Hz component during mental arithmetic was se condary to the changes in respiratory pattern or whether it reflected a direct task-related effect on the cardiac rhythm. ECG and respiratio n were recorded in five min periods of rest and mental arithmetics in thirteen young males. The respiratory signals were tape recorded in bo th periods. The subjects were then asked to reproduce by their breathi ng the previously recorded respiratory signals which were presented in the form of a moving horizontal bar on the oscilloscope screen. It wa s assumed that if a decrease of the 0.1 Hz component in mental arithme tics compared with rest was secondary to the changes in respiratory pa ttern then a similar decrease would be observed in the periods of repr oduction of the mental arithmetic pattern compared to reproduction of the resting pattern. The subjects reproduced the resting respiratory p attern and the mental arithmetic respiratory pattern faithfully. The s pectral parameter of the 0.1 Hz component was lower in mental arithmet ics than at rest but the same amplitude difference was found in the tw o reproduction periods indicating that a decrease in amplitude of the 0.1 Hz component during mental arithmetics could be attributed to the changes in respiration.